How Old are the Rocky Mountains?

Written by Megan Martin
Published: June 25, 2022
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The Rocky Mountains are one of the most popular mountain ranges in North America.

©Paul Brady Photography/

Thanks to the rise of new popular shows and documentaries detailing prehistoric life, more and more people are interested in learning about the history of our planet. While you may be more familiar with certain plants or animals, many people don’t understand just how old certain parts of the earth are. For instance, how old are the Rocky Mountains? If you don’t have an answer to this question, don’t worry: you will by the time you’re finished reading.

Ready to learn how old the Rocky Mountains are and more? Let’s dive in!

What are the Rocky Mountains?

Palisades Reservoir

Palisades Reservoir is a popular ice fishing spot in the Rocky Mountains near the Wyoming border.

© Botello

Before learning how old the Rocky Mountains are, you may be wondering what exactly are the Rocky Mountains. If you live in the western United States or even some parts of Canada, you may be familiar with them!

The Rocky Mountains, also known simply as the Rockies, are a major mountain range. In Cree, their name is As-sin-wati. They’re one of the largest ranges in the world and the largest in North America. The Rockies stretch from Canada down to New Mexico, crossing through Washington, Idaho, Montana, Wyoming, Utah, and Colorado in the process. 

How Old are the Rocky Mountains?

Now that you know a little bit more about what they are, it’s time to dive into the most important question. How old are the Rocky Mountains?

However, it’s not as simple as a question as one might think.

There are actually two ages to consider when thinking about how old they are. There’s the age of the mountains themselves, but there’s also the age of the rocks that make up the mountains.

Some of the rocks that make up the Rockies can date back to the Precambrian era. This is considered the earliest period, as far as we know right now. Some of the Precambrian rocks and sediment here can date as far back as 1.7 billion years ago! You can also find more recent layers, such as limestone and dolomite. These formed during the Paleozoic era when most of western North America as we know it today was actually underwater. The Paleozoic era occurred in the same eon that we currently live in, although it still dates back to millions of years ago.

However, while the rocks and sediment that make up the Rocky Mountains are billions are years old, the range itself is just a bit younger than that. The Rocky Mountains formed during the Laramide orogeny, which was a time when most of the mountains in the west formed. This means that they started to form around 80 million years ago and finished forming around 35 million years ago. 

Are the Rocky Mountains the Oldest Mountain Range?

The Rocky Mountains are home to many beautiful lakes and nature areas.


Despite being anywhere from 35 to 80 million years old, the Rocky Mountains actually aren’t the oldest range in the world. That award, instead, goes to the Barbertown Greenstone Belt, also known as the Makhonjwa Mountains. 

The Makhonjwa Mountains are found in Africa, on the eastern edge of Kaapvaal Craton in South Africa, to be specific. They’re known for gold, ancient fossils and volcanic rock. The Isua Greenstone Belt in Greenland has older rocks, but the Makhonjwa Mountains are considered older. 

Are the Rocky Mountains Older than the Appalachian Mountains?

Mount Mitchell North Carolina

The Appalachian Mountains are some of the oldest in the world.

© Flagstad

The Rocky Mountains are also much younger than the Appalachian Mountains or Smokies, another North American mountain range.

While the Rockies formed in the last tens of millions of years, the Smokies date back to nearly 500 million years ago. Not only are the Smokies older than the Rockies, however, but they’re also older than many of the other ranges on the planet. 

How Do Mountains Form?

Mountains form when continental plates meet.


Have you ever wondered how mountains form? If so, you’re not alone.

The Rocky Mountains and other ranges all tend to form in the same way. Usually, a mountain range occurs when two continental plates meet. Imagine you have two sheets of paper. If you were to slide these sheets of paper across a table so that they met with a great force, chances are, they would buckle and rise off the table together. This is the same with continental plates. When they collide, they force the earth upwards, resulting in the amazing mountains we see today. 

However, this can only work if the plates are around the same size. Think, if you replaced one of those pieces of paper with a sheet of cardboard. Instead of meeting and buckling, the paper would most likely just slide under the cardboard. 

Are the Rocky Mountains Changing?

Blanca Peak Colorado

The Rocky Mountains are constantly changing!


While the Rocky Mountains aren’t living creatures, they’re alive in their own way.

Ever since their formations tens of millions of years ago, they have continued to change. Some studies have even shown that the Rocky Mountains are still rising, while other forces, like erosion, change the shape. Human influence, such as mining and hiking, can also change the Rockies. 

The photo featured at the top of this post is ©

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About the Author

Megan is a writer at A-Z Animals where her primary focus is birds, felines, and sharks. She has been researching and writing about animals for four years, and she holds a Bachelor of Arts in English with minors in biology and professional and technical writing from Wingate University, which she earned in 2022. A resident of North Carolina, Megan is an avid birdwatcher that enjoys spending time with her cats and exploring local zoological parks with her husband.

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